Wide temperature range alkali metal grease containing excess alkali metal hydroxides



United States Patent WIDE TEMPERATURE RANGE ALKALI METAL GREASE CQNTAINING EXCESS ALKALI METAL HYDROXIDES John P. Dilworth, Fishkill, George W. Eckert, G-lenham, and William J. Coppoc, Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application April 27, 1951, Serial No. 223,431

13 Claims. (Cl..25233.3)

This invention relates to ball and roller bearing greases which are characterized by high dropping points and outstanding performance over a wide temperature range. The novel alkali metal greases of this invention are suitable for operation at temperatures as low as 20 F. and as high as 500 F., and higher.

The novel wide temperature greases of this invention result from elevated temperature digestion of a mixture comprising mineral oil, alkali metal soaps of a fatty material of prescribed composition, and a critical amount of excess alkali metal hydroxide. The critical factors in the production of the wide temperature range greases of this invention are a critical quantity of excess alkali metal hydroxide present during the high temperature digestion, the composition of the fatty material from which the alkali metal soaps are formed, the temperature and duration of the high temperature digestion, and rapid chilling plus milling of the drawn grease.

The novel greases of this invention are prepared :by digesting at a temperature of 480 to 550 F. for a period of 2 to 5 hours a dehydrated reaction mixture comprising to 25 per cent alkali metal soaps of a fatty material having an iodine number of at least 90, 60 to 80 per cent mineral oil and 1.7 to 2.3 per cent alkali metal hydroxide. After digestion at the prescribed temperature, additives, such as aluminum stearate, which imparts water resistance, are incorporated in the grease mixture which is then stirred for an additional period of minutes to 60 minutes prior to drawing at a temperature of about 500 F. The drawn grease is rapidly cooled in pans or in a rotary chiller whereby the grease is converted to a hard grease. Milling of the rapidly cooled hard grease in a roller mill or in a colloid mill produced smooth, glossy, hard greases Which are characterized by dropping points over 500 F., good oxidation resistance and excellent low temperature torque properties.

The alkali metal greases of this invention are important additions to the field of commercial greases. The high dropping points and good low temperature torque properties of the alkali metal greases of this invention adapt them for use over a Wide temperature range. The sodium base greases of this invention are particularly useful commercial greases. Sodium base greases of the composition prescribed in this invention are smooth, glossy greases with dropping points over 500 F. The preparation of alkali metal greases characterized by the aforesaid properties represents a significant advance in the art of grease making.

Naphthene base oils or paraffin base oils can be employed to prepare the novel alkali metal greases of this invention. With the parafiin base oils it is necessary to incorporate petroleum mahogany sulfonate salts as stabilizing agents in order to obtain suitable greases. Sodium petroleum mahogany sulfonate is ordinarily employed as the stabilizing agent. With parafiin base oils the added petroleum mahogany sulfonate salt amounts to about 0.25 to 4 per cent of the final calculated grease composition. The sodium petroleum mahogany sulfonate is added to the reaction mixture together with the paraffin base oil and is present during saponification and dehydration of the reaction mixture. When naphthene base oils, commonly known as pale oils, are employed, it is not necessary to employ stabilizing agents such as petroleum mahogany sulfonate salts since greases of high stability are prepared without the use of a stabilizing agent.

The mineral oil content of the novel greases of this invention comprises 60 to per cent of the total calculated grease composition. Advantageously, the mineral oil content comprises approximately 65 to 75 per cent of the total grease composition.

Soap-forming materials possessing a substantial olefin content are required for the formation of the alkali metal greases of this invention. The soap-forming stock, which can be soap-forming fatty acids, fatty esters or mixtures thereof, should possess an iodine number of at least and preferably between 90 and 130.

A particularly preferred soap-forming material comprises a mixture of menhaden oil and hydrogenated fish oil fatty acids, which latter are commercially known as Snodotte acids. A 3 to 1 menhaden oil-Snodotte acid mixture having an iodine value of approximately has proven particularly useful as a soap-forming stock.

Commercially available Snodotte acids have approximately the following soap composition:

Typical tests on commercially available Snodotte acids are as follows:

Sap. No 197 Neut. No 193 Iodine No 1 Titer, C 54.6

Other unsaturated soap-forming acids and esters having an iodine number higher than 90, such as castor oil, linoleic and linolenic acids, are also useful in the preparation of greases of this invention.

The soap-forming material of this invention is employed in such amounts that the alkali metal soap content of the final grease composition comprises approximately 15 to 25 per cent of the total grease composition. Ordinarily the soap content of the grease is within the range of 18 to 2-2 per cent.

As indicated previously, the concentration of excess alkali metal hydroxide present during the elevated temperature digestion is critical and lies in a very small range. It is necessary to maintain concentration of excess alkali between 1.7 and 2.3 per cent of the final calculated composition of the grease in order to produce a high dropping point grease. If the excess alkali metal hydroxide concentration is below or above the prescribed range, there is a significant lowering of the dropping point of the product grease.

The stoichiometric quantity of caustic required to neutralize the soap-forming material and the critical amount of excess alkali metal hydroxide are added to the grease mixture prior to saponification. Advantageously the total alkali metal hydroxide, comprising the stoichiometric quantity required to neutralize the soap-forming material and the critical amount of excess caustic, is added to the reaction mixture in the form of a saturated aqueous solution.

The novel greases of this invention may be prepared mineral oil, alltali metal soaps and excess caustic are also decisive in determining the quality of the greases. The digestion must be effected at temperatures between 4-80 and 550 F. to produce greases characterized by dropping points over 500 F. and good low temperature tor ue properties. A temperature between 500 and 550 F. is particularly preferred for the digestion. A digestion period of 2 /2 to hours is prescribed but digestion times of 3 to 4 hours have proven particularly advantageous.

After the grease mixture has been digested at a temperature of 480 to 550 F. for the prescribed period, various additives are blended into the greases at a temperature above 500 F. Diphenylamine, an oxidation inhibitor, and aluminum stearate, which imparts water resistance, are incorporated in the greases at a temperature of about 500 F. The total additive concentration is in the range of 1 to per cent of the final calculated grease composition. Ordinarily, diphenylarnine comprises 0.5 to 3 per cent whereas aluminum stcarate comprises 3 to 7 per cent of the final calculated grease composition.

After the additives have been thoroughly mixed into the grease at a temperature of about 450 to 550 F., the mixture is rapidly cooled. The resulting greases are hard and show little tendency to separate oil and possess excellent high temperature properties but are not useable in this condition at low temperatures. Milling the hard greases in a roller mill or in a colloid mill produces smooth, glossy greases which possess excellent low temperature torque characteristics and good oxidation resistance in addition to high dropping points.

The conversion of the hard block greases into wide temperature range greases by milling is unique and entirely unexpected. It is theorized that the high temperature digestion of the alkali metal soap of the olefinic fatty material in the presence of the prescribed critical amount of excess alkali metal hydroxide is responsible for this unique conversion of a block grease into a wide temperature range ball and roller bearing grease by the simple expedient of milling the rapidly chilled grease.

Rapid cooling of the additive-containing drawn grease mixture can be effected in a number of different ways. The hot grease at a temperature of about 500 F. can be drawn into pans and shock-chilled by indirect contact with cold water. An alternative means of rapid cooling involves the use of a rotary chiller in which the grease is forced through a small conduit or plurality of small conduits by helical screws in indirect contact with a cooling medium. The latter procedure is preferred for continuous manufacture.

The saponification procedure employed in the manufacture of the greases of this invention is eifccted at conventional conditions. The mineral lubricating oil fraction and the soap-forming stock are heated with stirring to a temperature of approximately 125 to 160 F. to effect good distribution of the reagents. If a parafifin base mineral oil is employed, the stabilizing mahogany sulfonate salt is added to the mixture at this time. At approximately 150 F., the alkali metal hydroxide containing the stoichiometric amount for saponification and the prescribed excess is added to reaction mixture in the form of an aqueous solution. In small scale preparations a small amount of silicone anti-foam agent may be added together with the caustic solution to minimize foaming. The saponifieation is efifectcd at a temperature between 150 and 200 F. in about one hour.

Dehydration of the saponified reaction mixture is effected at a temperature between 290 and 350 F. and ordinarily takes approximately 1 to 2 hours. The preferred temperature range for dehydrating the saponification mass is from 300 to 330 F.

The manufacture of the greases of this invention is illustrated in Examples 1 and 2. Example 1 illustrates the use of a roller mill for milling the rapidly chilled hard grease and Example 2 illustrates the use of a colloid mill in preparing the greases of this invention.

Example 1 A mixture of 18 lbs. of SAE grade 20 paraffinic mineral lubricating oil, 1.8 lbs. of pale oil solution containing 30.5 weight per cent sodium petroleum mahogany sulfonate, 11.6 lbs. of a 3 to 1 mixture of menhaden oil- Snodotte acids were charged to a fire-heated kettle wherein they heated with stirring to a temperature of about F. at which temperature 6 grams of methyl silicone (Dow Corning Anti-foam A) dissolved in 10 cc. of 20 grade paraffin oil was added. After 1 /2 hours of stirring and heating the addition of 1668 cc. of 50.4 per cent solution of sodium hydroxide was initiated at a temperature of about 300 F., the total caustic solution was added over a 2 1 hour period during which the temperature of the reaction mixture had risen to about 430 F. The added caustic comprised stoichiometric amount required to saponify the soap-forming constituents and in addition 1.9 per cent excess sodium hydroxide. After all the caustic had been added, 22.48 lbs. of SAE grade 20 paraliinic lube oil was added over a twenty-minute period. The temperature was then raised to 500 F. and held at this temperature for about three hours after which 3 lbs. of aluminum stearate were added over a ten minute period followed by the addition of 0.6 lb. of diphenylamine. Approximately, l5 minutes after the addition of the additives when the temperature of the grease mixture was about 470 F. the grease was drawn into pans and quickly chilled to form a hard block-type grease. On milling of the drawn, quickchilled grease by two passes through a 6" x 12" Thropp roller mill at room temperature there was obtained a grease having the following calculated composition:

Percent Na 3:1 menhaden oil-Snodotte acid soap 20.2 Excess NaOH in charge 1.9 Glycerin (from fat) 1.6

Paraifinic mineral oil, SAE 20 67.3

Aluminum stearate 5.0 Sodium petroleum mahogany sulfonate 3.0 Diphenylamine 1.0

The properties of the grease thus prepared are as follows:

Appearance, smooth, glossy, hard.

Dropping point, F. 500+ Unworked pene 182 Worked pene. 184

LOW Temp. Torque, Sam/rev. at cw. cow.

Dynamic water resistance, percent loss 22,8-25.8 Norma Hoffman oxidation, lb./ drop in 500 hr 8-10 Dynamic shear test:

Miniature penetration before 39-41 Miniature penetration after -169 1 Miniature Penetrolneter for Determining the Consistency of Lubricating Greases." Ind. Eng. Chem, analytical edition, vol. 11, page 108, February 15, 1930.

Example 2 The drawn, quick-chilled grease prepared in accordance with the procedure set forth in Example 1 was milled by passage through a Premier colloid mill which was rotated at 7200 R. P. M. with a clearance of 0.003 inch and an outlet temperature of 230 F. The efiiluent milled grease, which was somewhat aerated and colored brown to tan, was mashed to a homogeneous mass by hand working to yield a grease having a composition similar to that of the grease prepared in Example 1. The properties of the grease thus prepared are as follows:

Appearance, smooth, glossy, hard.

Norma Hoffman oxidation, lb./ drop in 500 hr 10-10 Dynamic sheer test:

Miniature penetration before 4448 Miniature penetration after 137-146 The foregoing examples illustrate the excellent wide temperature range ball and roller bearing alkali metal grease of this invention. The high dropping point, the good low temperature torque properties and the oxidation resistance are particularly significant. The wide temperature range ball and roller bearing alkali metal greases of this invention find a wide variety of uses because of their excellent properties.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A wide temperature range ball and roller bearing grease characterized by high dropping point, good oxidation resistance and low temperature torque properties which comprises a mixture of 15 to 25 percent alkali metal soaps of a soap-forming material having an iodine number of at least 90, 60 to 80 percent mineral oil, 1.7 to 2.3 percent alkali metal hydroxide, said grease having been prepared by incorporating said soap-forming material in said mineral oil, adding to said mixture an amount of alkali metal hydroxide equivalent to the sum of stoichiometric quantity required for saponification plus the prescribed excess alkali metal hydroxide, saponifying said mixture, raising said mixture to a temperature of 480 to 550 F., digesting the mixture at a temperature of 480 to 550 F. for 2 /2 to hours, drawing said grease at a temperature of about 500 F., rapidly chilling said drawn grease and milling said chilled grease.

2. A wide temperature range ball and roller bearing grease characterized by high dropping point, good oxidation resistance and low temperature torque properties which comprise a mixture of 15 to 25 percent alkali metal soaps of a 3 to 1 mixture of menhaden oil and hydrogenated fish oil fatty acids, 60 to 80 percent mineral oil, and 1.7 to 2.3 percent alkali metal hydroxide, and said grease having been prepared by incorporating said soap-forming material in said mineral oil, adding to said mixture an amount of alkali metal hydroxide equivalent to the sum of stoichiometric quantity required for saponification plus the prescribed excess alkali metal hydroxide, saponifying said mixture, raising said mixture to a temperature of 480 to 550 F., digesting the mixture at said temperature of 480 to 550 F. for 2 /2 to 5 hours, drawing said grease at a temperature of about 500 F., rapidly chilling said drawn grease and milling said chilled grease.

3. A grease according to claim 2 wherein sodium soaps are employed.

4. A wide temperature range ball and roller bearing grease characterized by high dropping point, good oxidation resistance and low temperature torque properties which comprises a mixture of 15 to 25 percent alkali metal soaps of a soap-forming material having an iodine number between 90 and 130, 60 to percent paraffinic mineral oil, 0.25 to 4 percent petroleum mahogany sulfonate salt, 1.7 to 2.3 percent alkali metal hydroxide, and 1 to 10 percent additives, said grease having been pre' pared by incorporating said soap-forming material in said mineral oil, adding to said mixture an amount of alkali metal hydroxide equivalent to the sum of the stoichio= metric quantity required for saponification plus the prescribed excess alkali metal hydroxide, saponifying said mixture, raising said mixture to a temperature of 480 to 550 F., digesting the mixture at said temperature of 480 to 550 F. for 2% to 5 hours, incorporating said additives in said digested mixture at a temperature of about 500 F. with stirring, drawing said grease at a temperature of about 500 F., rapidly chilling said drawn grease and milling said chilled grease.

5. A grease according to claim 4 wherein the soapforming material which comprises a 3:1 mixture of menhaden oil and hydrogenated fish oil fatty acids.

6. A grease according to claim 4 wherein the additives are diphenylamine and aluminum stearate.

7. A grease according to claim 4 wherein the excess alkali metal hydroxide content is about 1.9 per cent.

8. A wide temperature range ball and roller bearing grease characterized by high dropping point, good oxidation resistance and low temperature torque properties which comprises a mixture of 15 to 25 per cent sodium soaps of a 3:1 mixture of menhaden oil and hydrogenated fish oil fatty acids, said mixture having an iodine number of about 110, 60 to 80 per cent paraflinic mineral oil, 0.25 to 4 per cent sodium petroleum mahogany sulfonate, 1.7 to 2.3 per cent sodium hydroxide, 0.5 to 3 per cent diphenylarnine and 3 to 7 per cent aluminum stearate, said grease having been prepared by incorporating said menhaden oil-hydrogenated fish oil fatty acid mixture in said paraffinic oil, adding to said mixture an amount of sodium hydroxide equivalent to the sum of the stoichiometric quantity required for saponification plus the prescribed excess sodium hydroxide, raising said mixture to a temperature of 480 to 550 F., digesting the mixture at said temperature of 480 to 550 F for a period of 3 to 4 hours, incorporating said diphenylamine and aluminum stearate in said mixture with stirring at a temperature of about 500 33., drawing said grease at a temperature of about 500 F., rapidly chilling said drawn grease and subjecting said chilled grease to milling.

9. A grease according to claim 8 in which approximately 1.9 per cent excess sodium hydroxide is employed.

10. A grease according to claim 9 wherein the final grease composition comprises about 20 per cent sodium soaps of the 3:1 mixture of menhaden oil and hydrogenated fish oil fatty acids, about 70 per cent SAE grade 20 parafiinic oil, 1.9 per cent excess sodium hydroxide, about 1.5 per cent sodium petroleum mahogany sulfonate, about 5 per cent aluminum stearate and about 1 per cent diphenylamine.

11. A process for preparing alkali metal greases characterized by high dropping point, good oxidation resistance and low temperature torque properties which comprises digesting at an elevated temperature of 480 to 550 F. for a period of 2%. to 5 hours a saponified dehydrated mixture comprising 15 to 25 per cent alkali metal soaps of a soap-forming material having an iodine number of at least 90, 60 to 80 per cent mineral oil and 1.7 to 2.3 per cent excess alkali metal hydroxide, drawing said grease at a temperature of, about 500 F., rapidly chilling said drawn grease and subjecting said rapidly chilled grease to milling to produce a smooth glossy grease useable over a Wide temperature range.

12. The process according to claim 11 in which diphenylamine and aluminum stearate are added to the 7 grease mixture at a temperature of about 500 B, after the elevated temperature digestion and prior to drawing said grease.

13. A process for preparing alkali metal greases characterized by high dropping point, good oxidation resistance and low temperature torque properties which comprises digesting at an elevated temperature of 480 to 550 F. for a period of 2 /2 to 5 hours a saponified dehydrated mixture comprising to per cent alkali metal soaps of a 3 to 1 mixture of menhaden oil and hydrogenated fish oil fatty acids, to per cent mineral oil and 1.7 to 2.3 per cent excess alkali metal hydroxide, drawing said grease at a temperature of about 500 R, rapidly chilling said drawn grease and subjecting said rapidly chilled grease to milling to produce a smooth glossy grease useable over a wide temperature range.

References Cited in the file of this patent UNITED STATES PATENTS 2,265,791 Zimmer et a1 Dec. 9, 1941 2,351,384 Woods June 13, 1944 2,387,170 Morgan Oct. 16, 1945 2,394,790 Liehe Feb. 12, 1946 2,468,098 Morway et a1. Apr. 26, 19 2,495,651 Butcosk Jan. 24, 1950 2,503,969 Rudel et a1. Apr. 11, 1950 2,514,286 Morway et a1. July 4, 1950 2,542,570 Puryear ct a1. Feb. 20, 2,566,793 Davies Sept. 4, 1951 2,595,161 Morway et a1. Apr. 29, 1952 

1. A WIDE TEMPERATURE RANGE BAIL AND ROLLER BEARING GREASE CHARACTERIZED BY HIGH DROPPING POINT, GOOD OXIDATION RESISTANCE AND LOW TEMPERATURE TORQUE PROPERTIES WHICH COMPRISES A MIXTURE OF 15 TO 25 PERCENT ALKALI METAL SOAPS OF A SOAP-FORMING MATERIAL HAVING AN IODINE NUMBER OF AT LEAST 90, 60 TO 80 PERCENT MINERAL OIL, 1.7 TO 2.3 PERCENT ALKALI METAL HYDROXIDE, SAID GREASE HAVING BEEN PREPARED BY INCORPORATING SAID SOAP FORMING MATERIAL IN SAID MINERAL OIL, ADDING TO SAID MIXTURE AN AMOUNT OF ALKALI METAL HYDROXIDE EQUIVALENT TO THE SUM OF STOICHIOMETRIC QUANTITY REQUIRED FOR SAPENIFICATION PLUS THE PRESCRIBED EXCESS ALKALI METAL HYDROXIDE, SAPENIFYING SAID MIXTURE, RAISING SAID MIXTURE TO A TEMPERATURE OF 480 TO 550* F., DIGESTING THE MIXTURE AT A TEMPERATURE OF 480 TO 550* F. FOR 21/2 TO 5 HOURS, DRAWING SAID GREASE AT A TEMPERATURE OF ABOUT 500* F., RAPIDLY CHILLING SAID DRAWN GREASE AND MILLING SAID CHILLED GREASE. 